52 THE STUDY O F PLANT COMMUNITIES * Chapter III 



TABLE 1. Average density (D) and cover (C), by zones, of principal 

 species mapped on a transect from high tide to the crest of the rear dune at 

 Ft. Macon, N. C. (see Fig. 20). Both cover and density values show the pre- 

 dominance of Uniola in exposed zones and of Andropogon in protected ones. 

 This is correlated with salt spray. 188 



species. Transects are also useful in altitudinal studies and in any 

 situation where transitions between communities occur. 



Sizes of transects, just as sizes of quadrats, will be determined 

 by conditions. A transect reaching from one small community to 

 another, across a transition zone, might need to be only a few 

 meters long and perhaps a meter or less in width. Transects from 

 lake margins across the several marginal girdles of vegetation that 

 are usually present might be much longer. One reaching from 

 high-tide mark across seaside dunes might be several hundred 

 meters long. A study of the zonation of vegetation on the Sierra 

 Nevada was made by mapping a transect seven miles wide and ex- 

 tending across the mountain range for a distance of eighty miles. 144 



When it seems desirable to map an entire transect in detail, it is 



